// 读取 price、weight、s；按距离区间计算 discount，输出 freight=price*weight*s*(1-discount)
#include <stdio.h>

int main(void)
{
    double price, weight, s;
    if (scanf("%lf %lf %lf", &price, &weight, &s) != 3) {
        return 0;
    }

    double discount;
    if (s < 250.0) {
        discount = 0.0;
    } else if (s < 500.0) {
        discount = 0.02;
    } else if (s < 1000.0) {
        discount = 0.05;
    } else if (s < 2000.0) {
        discount = 0.08;
    } else if (s < 3000.0) {
        discount = 0.10;
    } else {
        discount = 0.15;
    }

    double freight = price * weight * s * (1.0 - discount);
    printf("freight=%.2f", freight);
    return 0;
}